As known in the art, an insulator is disposed for insulation between a stator core and a stator coil of a rotary electric machine. The insulator is usually shaped into a substantially rectangular sleeve having a hole in which a tooth is received. The insulator is attached to the tooth by hooking engagement tabs formed on side surfaces of the insulator into engagement recesses formed in side surfaces of the tooth.
The stator core is a stack of a plurality of electromagnetic steel sheets, each electromagnetic steel sheet having notches for forming the engagement recesses. More specifically, each electromagnetic steel sheet has a plurality of tooth portions that form teeth when the electromagnetic steel sheets are stacked, each tooth portion having substantially rectangular notches on both sides of the tooth portion. By stacking such electromagnetic steel sheets, engagement recesses shaped in grooves extending throughout the stator in the axial direction are formed on both sides of each tooth.